Self-projectable element for a space vehicle



June 17, 1969 m LANGE ET L 3,450,312

SELF-PROJECTABLE ELEMENT FOR A SPACE VEHICLE Filed Feb. 4, 1966 INVENTOR.

R. G. DE LANGE C. A. VERBRAAK J. A. ZIJ

ATTORNEY United States Patent 3,450,372 SELF-PROJECTABLE ELEMENT FOR A SPACE VEHICLE Robert Gerardus de Lange, Reeuwijk, Cornelis Antonius Verbraak, Beekbergen, and Jacobus Antonius Zijderveld, Zoetermeer, Netherlands, assignors to N ederlandse Organisatie voor Toegepast- Natuurwetenschappelijk Onderzoek ten behoeve van Nijverheid, Handel en Verkeer, a corporation of the Netherlands Filed Feb. 4, 1966, Ser. No. 525,177 Claims priority, application Netherlands, Feb. 10, 1965, 6501606 Int. Cl. B64c 39/00; H01q 1/28; H04b 1/38 U.S. Cl. 244-1 3 Claims ABSTRACT OF THE DISCLOSURE A space vehicle provided with at least one device adapted to be projected from the body of the vehicle in order to perform a function as an aerial, an antenna, a reflector, a solar battery, a rotation-reducing or stabilizing means, or as a carrier of any of these, said device comprising at least one wound-up element made of a ubstantially equi-atomic nickel-titanium alloy adapted to be unfolded substantially under the influence of special heat radiation. Such devices include coils which unroll around their axes and/ or axially to form hollow helicoidal shapes or hollow cones. These devices when in their coiled position may be located within cavities in the space vehicle, that is below its outer surface, and be projected beyond the surface either by their own action to heat radiation, or together with mechanical means initiated by a signal, or they may even be wrapped around a cylindrical portion of the space vehicle itself.

RELATED APPLICATION Netherlands application Ser. No. 6,501,606, filed Feb. 10, 1965, from which the present application claims priority.

BACKGROUND OF INVENTION Space vehicles provided with such projecting devices or elements are known. While the vehicle is being launched and is gathering height the elements are in a screened-off position in or on the vehicle and they are projected at the desired moment.

Aerials are known, which are kept agains the body of the vehicle by wires, which are released at the required time and which unfold under the influence of the centrifugal force.

Reflectors are known comprising segments folded one against the other, each of which is fastened about a centre of rotation and which after a definite signal are rotated by a motor and are unfolded.

There is also known a hollow aerial carrier, which is wound up as a fiat spiral, and which is unrolled, inflated, and filled with stiffening foam with the aid of a pressure medium containing a foam generator.

In addition to this there is known a projection containing a spring. which, in its compressed state, is surrounded by a material, which can sublime and which when subliming loses its grip on the spring, causing the latter to unbend and assume a sretched shape.

Lastly, there is known a strip-shaped element of spring steel or beryllium-copper alloy, which wound on a drum together with a tape. The element is unrolled by a motor which pulls off the tape and conveys the strip through a guiding means, to straighten the strip and bend about its longitudinal axis so as to form a tube having inherent rigidity.

With all of these elements, special provisions have been applied in the space vehicle for projecting or withholding the elements. These provisions take up room and may become a source of disturbance.

SUMMARY OF INVENTION The present invention relates to elements, such as for a space vehicle which elements can be projected without auxiliary means being required to attain the desired straightening of the rolled device.

It is known that a nearly equi-atomic nickel-titanium alloy has a conversion-temperature range in which a straight wire made of said alloy above said range and coiled at room temperature spontaneously reassumes a straight shape when heated.

Thus the present invention is for devices which may at a given time or in a given situation, be projected, which devices mainly consist of an unwindable wire, strip, or foil made of nickel-titanium alloy having about equal atom percentages of nickel and titanium wherein the nickel does not exceed 60% by weight of the alloy. These devices, prior to being wound up, have been extended below their conversion-temperature ranges, and held in their stretched or extended state while being heated above and slowly cooled below their conversion-temperature ranges. When such a device or element is used in a space vehicle and is subjected to a rise in temperature, such as by exposure the sun, which temperature entirely or partly comprises its conversion-temperature range, the element or device spontaneously stretches itself, so that it projects outside the periphery or surface of the space vehicle.

BRIEF DESCRIPTION OF THE DRAWINGS The above menioned and other features and objects of this invention and the manner of attaining them will become more apparent and the invention itself will be understood best by reference to the following description of embodiments of the invention taken in conjunction with the accompanying drawing, wherein four of these embodiments are schematically shown on the partially sectioned outline of a space vehicle or satellite.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The elements per se The element is preferably constructed as a strip or foil, which in the stretched state is curved about its longitudinal axis to increase its rigidity. When equal atom percentage of nickel and titanium are used, the conversion-temperature range lies between 50 and centigrade.

An increase of the nickel content upwards of 60% by weight gives rise to difliculties in connection with the workability. It has been found that, by adding cobalt and/or iron to replace nickel and/ or adding aluminum to replace titanium, the conversion-temperature range may be lowered in such a manner that with percentages of the additional metals up to 1% of the total weight of the alloy, the range may be shifted to below ,0 to 40 centigrade. When the replacement is increased to over 1%, the conversion is suppressed and the power to restore itself disappears. This specific property of the material to revert back to its original form is partly lost when it is heated above 800 centigrade.

Therefore the cast material used as a starting point for the production of such projecting elements is rolled ino sheet material at a temperature below 800 centigrade and preferably below about 750 centigrade, after which heating up to 750 centigrade follows and renewed rolling into strips can be effected. Finally, it is also possible to cold-roll, provided that after the last passage of the rollers, annealing up to 750 centigrade and cooling in air takes place.

From the material thus obained an element is cut in the dimensions required, an elongated thin strip being preferred. The strip should be brought into the shape required as the projected element below the lowest temperature of the conversion-temperature range, the shape preferably having a curved transverse cross-section, like a coilable metal measuring tape, like a portion of a tube or cone, or like a helicoidally wound strip. In this extended shape the strip is clamped fast and subjected to a temperature in excess of the conversion-temperature range. After a temperature upwards of the highest conversion temperature has been reached in all and every part of the strip, the latter while still being held is cooled to below the lowest conversion temperature by cooling in the air. From the shape obtained in this manner the cooled strip below its conversion temperature range can be physically changed into a different form, for instance by rolling or winding it up into one of the above mentioned shapes. In this manner even a very drastic change of shape may be made, provided that no sharp creases or bucklings are made.

Uses of the elements Thus, after it has been wound or rolled up into a minimal spacial dimension, the element may be positioned in a space vehicle as shown in the drawings and connected up. In one embodiment 10, the exterior end 12 of a coiled element 13 is fixed to the vehicle 1 in such a way that the axis of the coil 13 is parallel to the surface from which the element is to be projected and that the direction of unfolding is perpendicular to the said surface. The element may fit into a cavity 2 in the vehicle 1, the outer open side of which cavity 2 may be screened off from the radiation during the launching and while the space vehicle is gathering height. Then when the shields are shed, as soon as the vehicle has reached a part of its orbit, in which the frictional resistance of the atmosphere has fallen below a certain value, the winding 13 is exposed to the radiation of the sun or of some other celestial body. This causes the temperature of the outermost turns of the coil or winding 13 to raise and soon as the conversion-temperature range has been reached, these turns are stretched one after another. The part which is still rolled up moves out of the cavity 2 and away from the vehicle and gradually all of the turns are exposed and thereby stretched, and the element 10 reaches its completely outstretched state.

In another embodiment of the invention, a coil or winding 23 may be wrapped around a cylindrical portion 3 of the space vehicle 1 itself and may unfurl and stretch itself like a flag 24. In a further embodiment 30, the coiled strip 33 may be fixed to a shaft 35 by its innermost turn 36, and be accommodated in a cavity 4 inside the space vehicle. Upon a signal, the shaft 35 is projected, such as by a piston or rack and pinion 37 and 38, from the cavity 4 and out from the surface of the vehicle 1 so that the turns 33 then can be exposed to radiation, and spontaneously unfurl like a flag or pennant 39.

A still further embodiment shows an element 40 that has been rolled up like a spiral 47, which when unfolded, stretches itself out of its cavity 5 in the vehicle 1 axially relative to the axis of the winding so as to form a helicoidal tube 48 with a diameter which decreases or increases) towards its projected end 49.

It is also possible to construct a composite element consisting of a number of strips or foils, which after heating unfold into one or more screens. It may be useful to intensify the initiation of the unfolding by providing a heating source in the space vehicle, for instance for bringing the element forward from a protected position. It is however essential that no auxiliary means must be provided for the stretching or unwinding of the devices in that the element derives its unfolding exclusively from its own characteristic material properties and at least from spacial radiation coming from outside itself or its vehicle.

The element itself may serve as an aerial, a reflector or a retarding or a stabilizing element, but it may function just as well as a carrier of these or a carrier of solar batteries, provided of course that the parts to be carried are dimensioned in such a manner that they dont form an impediment to the elements being in a wound-up state or to the unrolling movements to be carried out while the conversion-temperature range is being passed through.

Within the scope of the invention there also falls an element of the material described, in which this element, besides serving the purposes already mentioned, may also be constructed as a gripping or coupling element or may function as a carrier of the same. In this case, the gripping or coupling action may be obtained by giving that part of the element that is used for this action, for instance its extremity, a basic form which is not stretched but has, for instance, the shape of a hook, a gripper or a cup, which is opened, but which closes itself consequential to a rise in temperature. Such an element may 'be used an an anchor or a sampler on a celestial body.

We claim:

1. In a space vehicle, a temperature responsive selfprojectable device comprising:

a coil of an alloy of about equi-atomic percentages of nickel and titanium, said alloy containing less than 60% by weight of nickel, wherein said nickel is replaced by cobalt but not more than 1% by weight of said alloy,

which alloy prior to being coiled has been extended below its conversion temperature range and held in this extended state while being raised in temperature above its conversion temperature range and cooled slowly back to below this range,

weherby the heating of said coil by spacial radiation above its lowest critical temperature range causes said coil to unwind into its said extended state.

2. In a space vehicle, a temperature responsive selfprojectable device comprising:

a coil of an alloy of about equi-atomic percentages of nickel and titanium, said alloy containing less than 60% by weight nickel, wherein said nickel is replaced by iron but not more than 1% by weight of said alloy,

which alloy prior to being coiled has been extended below its conversion temperature range and held in this extended state while being raised in temperature above its conversion temperature range and cooled slowly back to below this range,

whereby the heating of said coil by special radiation above its lowest critical temperature range causes said coil to unwind into its said extended state.

3. In a space vehicle, a temperature responsive selfprojectable device comprising:

a coil of an alloy of about equi-atomic percentages of nickel and titanium, said alloy containing less than 60% by weight nickel, wherein said titanium is replaced by aluminum but not more than 1% by weight of said alloy,

which alloy prior to being coiled has been extended below its conversion temperature range and held in this extended state while being raised in temperature above its conversion temperature range and cooled slowly back to below this range,

whereby the heating of said coil by spacial radiation above its lowest critical temperature range causes said coil to unwind into its said extended state.

References Cited UNITED STATES PATENTS OTHER REFERENCES Journal of Applied Physics, vol. 34, N0. 5, May 5, 1963, pp. 1475-1477. Effect of Low-Temperature Phase Changes on the Mechanical Properties of Alloys Near 5 Composition TiNi.

Kamm 244 1 FERGUS S. MIDDLETON, Primary Examiner. Dickstein et a1. 244-1 Kershnen US. Cl. X.R.

Johnson et al. 10 7s 170;32s-15; 343405 

